After centuries of little progress, developments in the field of prosthetics have seismically transformed the lives of paralysed patients

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At the age of 18, Nathan Copeland was in a brutal car accident that broke his neck. He became a C5 level quadriplegic, one of the worst spinal cord injuries, and lost the ability to control his torso and his limbs—legs, wrists, and hands included. A decade later, his physical feeling of touch was restored through the use of a robotic hand, allowing him to in effect feel his fingers and hands for the first time in years. “Sometimes it feels electrical and sometimes it’s pressure, but for the most part I can tell most of the fingers with definite precision,” said Copeland in 2016. “It feels like my fingers are getting touched or pushed.”

It marked the first time a paralysed person experienced the sensation of touch through brain stimulation. Robert Gaunt at the Center for the Neural Basis of Cognition in Pittsburgh, Pennsylvania, and his team achieved this by implanting electrodes in the brain of Copeland, working in conjunction with his robotic hand and a linked computer. When blindfolded and put to the test, he correctly guessed which of the robotic hand’s fingers were being touched 80% of the time. In effect, the implant in Copeland’s brain allowed him to feel genuine sensations. He could touch again.

“I can feel just about every finger,” he added at the time. “It’s a really weird sensation.”

Rapid breakthroughs

After centuries of little progress, developments in the field of prosthetics design like those tested on Copeland have, in recent years, seismically transformed the lives of amputees and paralysed patients. The technologies of today permit a more advanced range of movement but also the advent of brain-controlled prosthetic limbs.

Estimates by Stanford University reveal that there are 10 million amputees worldwide, including more than 2 million in Europe, caused by everything from diabetes to car accidents and war. That number is on the rise, and with it an increased need to cater to those with a sensory perception outside of the norm.

What may seem like in practice simple and modest improvements in the capacity of individuals to go about their daily lives, these small steps are proving to be a transformative leap forward.

“It tends to be small things that have the biggest impact,” says Jay Burkholder, general manager for Mobius Bionics, who distribute Deka’s LUKE Arm, a sophisticated full arm prosthetic that incorporates 10 joint movements of the shoulder, elbow, hands and fingers. “One of our patient’s big things was fishing, so with his new arm, it meant so much that he could finally tie a fish hook. Another person cried after opening a water bottle—it’s almost impossible with just one hand, you need two hands to unscrew a lid.”

The Luke Arm. Image courtesy Mobius Bionics

According to Burkholder, the development of a brain-computer interface has progressed at lightning speed. As a consequence, haptic feedback, or sensory feedback as it is otherwise known, could be on the mass market within five years.

“It’s going to get closer and closer to the real deal,” he says. “People will live completely normal lives with bionic limbs. In fact, as they become lighter and more powerful, they will become stronger than human limbs. We’ll have exoskeletons lifting insane loads.”

Technological bottlenecks

One key bottleneck surrounds the complexities of touch, according to Dr. Sliman Bensmaia, an associate professor and neuroprosthetics researcher at the University of Chicago whose lab was recently awarded a US $3.4 million grant from the National Institutes of Health.

Humans normally have 10,000–15,000 nerve fibres to experience touch, which is at the heart of our dexterity, but current technology is limited to just hundreds of electrodes, a relatively small number.

“We are lacking in the technology with regard to these implants and their longevity at the moment,” he says. “But in the long term, this problem is definitely going to be solved. Sooner rather than later. Though there are also challenges posed by the brain, which is the most complex system in the known universe.”

Despite these future obstacles, a thriving cottage industry is researching a range of potential solutions.

Diverse solutions

PSYONIC, a startup based in Illinois, is making bionic limbs with a flesh-like feel that are 20% lighter than the average human weight yet cost a tenth of the price in raw materials of other prosthetics. Billionaire Elon Musk’s company Neuralink, meanwhile, is pioneering an interface that connects to the brain through dozens of thin wires and will eventually be small enough to sit inside the skull and transmit wirelessly. Meanwhile, Sweden’s Integrum, Australia’s Dr. Munjed Al Muderis and Switzerland’s SensArs are collectively pushing the field forward.

The latter was last month heralded for its success in combining with the Swiss Federal Institute of Technology to surgically connect a mechanical limb to nerve endings in the thighs of volunteers, according to research in the journal Nature Medicine. As well as providing greater stamina, stability and mobility, it reduced the phantom limb pain often suffered by amputees.

“We are constructing the game-changing improvement of the technology that will become the essential feature of the next-generation,” says Francesco Petrini, cofounder and CEO of SensArs. “There’s a very bright future.”